Blood products used for transfusion and production of blood components are screened for the presence of the viral pathogens HBV, HCV, HTLV-I and HTLV-II, HIV and CMV. Contamination by these pathogens is determined by the detection of viral antigens or anti-viral antibodies using EIA technology. Current tests are hindered in their ability to detect viral contamination of blood products during early infection prior to seroconversion by the inability to detect low viral concentrations or the inability to detect virus-immune complexes. The aim of this proposal is to develop an ultra-sensitive bead-based assay system for flow cytometry to detect viral antigens and host-derived anti-viral antibodies. Flow cytometers can multiplex analyses based on analysis of different fluorescence emissions. This will be used to develop assays capable of quantifying multiple viral antigens and antibodies simultaneously. Preliminary assays have been developed for HIV, HBV and HCV capable of simultaneous detection of two viral antigens and anti-viral antibody. Viral antigen detection has been demonstrated down to the sub-picogram/ml level. The focus of this proposal is to develop clinically useful assays for the simultaneous high sensitivity detection of viral pathogens and anti-viral antibodies. PROPOSED COMMERCIAL APPLICATION: To develop an ultra high sensitivity immunoassay that will be able to simultaneously detect the common viral pathogens screened for by blood banks (i.e.-HIV, HBV, HCV, HTLA, etc.) sensitivity and specificity levels far superior to current EIA technology and much faster and cheaper than PCR testing. This assay will be commercialized as a kit that cna be used on flow cytometers and potentially other fluorescence detection instruments.